1. Melt yeast in about 30g water, add 50g flour, knead into dough, cover with plastic film and ferment for 1 hour.
2. Knead the remaining flour and water into a hard dough. Cover with plastic film and let it stand for 30 minutes. Mix the dough with the hard dough. Knead on the panel repeatedly until the dough is smooth and tough.
3. Divide the dough into proper size, 4-6 portions. Then knead each piece separately, as shown in the figure, and roll it into a cake with a thickness less than 1cm with a rolling pin. Blanch the cake for 2-3 minutes until both sides are yellowish, about 80-90 ripe.